Field of the Invention
The present disclosure relates to a CT detection method and a CT device, and specifically relates to an image reconstruction method in an X-ray CT imaging system.
Description of the Related Art
A CT system is typically used in medical imaging devices and industrial detection arrangements, which scans an object to be detected by means of X-ray, images the object to be detected using scanning data, and thereby detects the interior of the object to be detected. It is necessary for the CT system to have a higher spatial resolution in case that measurement for geometric dimension of the object to be detected and detection for minor detects of the object to be detected are implemented using the CT system.
A patent document CN102525527A discloses a method of processing projection data, which adopts an X-ray computed tomographic device for imaging. The device includes a gantry, which accommodates an X-ray source and a two-dimensional array type X-ray detector. The X-ray source and the two-dimensional array type X-ray detector are installed on a rotating ring in facing opposite sides of a subject to be detected.
According to the method disclosed in the above patent document, the projection data are acquired using a cone beam along a circular trajectory, a weight value for said projection data is determined according to a normalized electrocardiogram gated reconstruction (EGR) weighting function WEGR(β,γ) based upon an EGR weighting function UEGR(Φ(β)), said UEGR(Φ(β)) is normalized by a summation of UEGR(Φ(βcn%)) from n=−NPI to n=NPI, where Φ is a cardiac phase, β is a view angle, βcn is a complementary view angle, PI=π; each of the projection data is weighted by said weight value as determined by said WEGR(β,γ), where γ is a fan angle of the cone beam.
However, the spatial resolution of the image obtained by means of the above method cannot meet the requirement for the above-described application.
Actually, spatial resolution is an important parameter for an X-ray CT system, which is limited by some hardware factors including, for example, focus size of a ray source, dimension of a detector, and magnification ratio of a scanning system, and the like.
The scanning system amplification ratio may be chosen based on various system parameters, as well as dimension of the object to be detected, as a result, the focus size of the ray source and the dimension of the detector form factors, which limit the spatial resolution of the system. In addition, in an industrial CT system, since X-ray has relatively high energy, the focus of the ray source is typically sized in a range of 1.0 mm to 2.0 mm, so as to meet the requirement for heat dissipation of target. However, the dimension of the detector unit is of the order of sub-millimeter, accordingly, the focus size of the ray source forms a major factor of limiting the spatial resolution of the CT system.